A waveform equalizer for removing multipath interference is mounted on a receiver for digital broadcasting and digital radio communication. Multipath interference is a phenomenon in which a plurality of signals transmitted through different paths reach a receiver and an interference signal (ghost) that interferes with a main signal to be received is observed. The waveform equalizer restores such an interfered main signal.
A pre-ghost and a post-ghost may be generated as an interference signal of multipath interference. A pre-ghost is a transmitted signal that reaches a receiver earlier than a main signal, while a post-ghost is a transmitted signal that reaches a receiver later than a main signal.
A waveform equalizer having an FIR (finite impulse response) filter and an IIR (infinite impulse response) filter is used to equalize a received signal that includes a pre-ghost and a post-ghost. An example of such a waveform equalizer is disclosed in Patent document 1. The waveform equalizer of Patent document 1 implements reduction in power consumption and circuit area by varying convolution operation accuracy according to a calculated operation accuracy control value.    Patent document 1: Japanese Laid-Open Patent Publication No. 2005-39687